Eldecalcitol (1α, 25-dihydroxy-2β-[3-hydroxypropyloxy] vitamin D3; ED-71) is an analog of the active form of vitamin D. Eldecalcitol has a hydroxypropyloxy group at the 2β-position of 1,25(OH)2D3. Compared with 1,25(OH)2D3, eldecalcitol has a higher affinity for serum vitamin D-binding protein (DBP), binds more weakly to vitamin D receptor, and shows lower potency in suppression of serum parathyroid hormone. The plasma half-life of eldecalcitol is longer than that of 1,25(OH)2D3, probably due to the higher affinity for DBP. In addition to regulation of calcium metabolism carried out by conventional vitamin D analogs, eldecalcitol possesses a strong inhibitory effect on bone resorption and causes a significant increase in bone mineral density. EDIROL (Eldecalcitol) has been approved for the treatment of osteoporosis in Japan.